Voltage Stability Analysis of Grid-Connected Wind Farms with FACTS: Static and Dynamic Analysis

Recently, analysis of some major blackouts and failures of power system shows that voltage instability problem has been one of the main reasons of these disturbances and networks collapse. In this paper, a systematic approach to voltage stability analysis using various techniques for the IEEE 14-bus case study, is presented. Static analysis is used to analyze the voltage stability of the system under study, whilst the dynamic analysis is used to evaluate the performance of compensators. The static techniques used are Power Flow, V–P curve analysis, and Q–V modal analysis. In this study, Flexible Alternating Current Transmission system (FACTS) devices- namely, Static Synchronous Compensators (STATCOMs) and Static Var Compensators (SVCs) - are used as reactive power compensators, taking into account maintaining the violated voltage magnitudes of the weak buses within the acceptable limits defined in ANSI C84.1. Simulation results validate that both the STATCOMs and the SVCs can be effectively used to enhance the static voltage stability and increasing network loadability margin. Additionally, based on the dynamic analysis results, it has been shown that STATCOMs have superior performance, in dynamic voltage stability enhancement, compared to SVCs

Short circuit study of fixed speed wind turbines with STATCOM in distribution networks

The increased penetration of wind farm in distribution networks has brought changes in the performance of the whole system. Such disadvantages when connecting one of these distributed generation sources is reduced voltage and power stability of the AC network. This phenomena can cause the connected electricity consumers to suffer from disturbances. This paper investigates the use of a static synchronous compensator (STATCOM) to improve the short circuit current contribution in the network which will include balanced and unbalanced faults. The wind farm is equipped with fixed-speed wind turbines driving squirrel-cage induction generators. The IEEE 30-bus distribution test system is used to see the performance of the system under distribution level. Simulation studies are carried out in the DIgSILENT software

Power Quality Improvement and Low Voltage Ride through Capability in Hybrid Wind-PV Farms Grid-Connected Using Dynamic Voltage Restorer

© 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission.This paper proposes the application of a dynamic voltage restorer (DVR) to enhance the power quality and improve the low voltage ride through (LVRT) capability of a three-phase medium-voltage network connected to a hybrid distribution generation system. In this system, the photovoltaic (PV) plant and the wind turbine generator (WTG) are connected to the same point of common coupling (PCC) with a sensitive load. The WTG consists of a DFIG generator connected to the network via a step-up transformer. The PV system is connected to the PCC via a two-stage energy conversion (dc-dc converter and dc-ac inverter). This topology allows, first, the extraction of maximum power based on the incremental inductance technique. Second, it allows the connection of the PV system to the public grid through a step-up transformer. In addition, the DVR based on fuzzy logic controller is connected to the same PCC. Different fault condition scenarios are tested for improving the efficiency and the quality of the power supply and compliance with the requirements of the LVRT grid code. The results of the LVRT capability, voltage stability, active power, reactive power, injected current, and dc link voltage, speed of turbine, and power factor at the PCC are presented with and without the contribution of the DVR system.Peer reviewe

Reactive Power Management at PCC with DFIG Based Wind Energy System

Reduction in availability of conventional energy sources and their scarcity in the future has led to the research on adoption of renewable energy sources for electricity generation. Wind is recognized as the prominent renewable energy source for electricity generation. Due to the erratic pattern of wind, variable speed generators such as doubly fed induction generator (DFIG) are preferred over fixed speed wind generators which use synchronous generators. Due to the increase in contribution of electricity generation through renewable energy sources, power quality of the system is deteriorating. In the present paper, a new economical and tangible scheme of DFIG is proposed to compensate for the reactive power at PCC, thus improving the power quality of the grid. The effectiveness of the scheme in compensating for the reactive power is evaluated using MATLAB / Simulink environment

Impacts of high penetration of DFIG wind turbines on rotor angle stability of power systems

With the integration of wind power into power systems continues to increase, the impact of high penetration of wind power on power system stability becomes a very important issue. This paper investigates the impact of doubly fed induction generator (DFIG) control and operation on rotor angle stability. Acontrol strategy for both the rotor-side converter (RSC) and grid-side converter (GSC) of the DFIG is proposed to mitigate DFIGs impacts on the system stability. DFIG-GSC is utilized to be controlled as static synchronous compensator (STATCOM) to provide reactive power support during grid faults. In addition, a power system stabilizer (PSS) is implemented in the reactive power control loop of DFIG-RSC. The proposed approaches are validated on a realistic Western System Coordinating Council (WSCC) power system under both small and large disturbances. The simulation results show the effectiveness and robustness of both DFIG-GSC control strategy and PSS to enhance rotor angle stability of power system

VAr Compensation Based Stability Enhancement Of Wind Turbine Using STATCOM

Maintenance of power system stability becomes vital during disturbances like faults, contingency etc. This work deals with a novel priority oriented optimal reactive power compensation of Doubly-Fed Induction Generator (DFIG) based wind turbine using Static Synchronous Compensator (STATCOM). A multi-objective problem will be formulated to maintain voltage within its tolerance levels using Voltage Severity Index (VSI) and to mitigate low frequency oscillations by using Transient Power Severity Index (TPSI) during post-fault conditions. An optimal solution to this proposed problem will be obtained using Fuzzy Logic. In order to justify the proposed methodology it is simulated and tested using 2 MW DFIG with MATLAB- Simulink.nbs

A Comparison Study of Reactive Power Control Strategies in Wind Farms with SVC and STATCOM

In the recent years, the integration of the wind farms into the electrical grids has increased rapidly. Especially, the wind power plants made up with doubly fed induction generators due to its many advatanges, such as being able to control its reactive power. Hence, some countries have published grid code requirements related to the reactive power that the wind turbines have to satisfy. This paper presents a coordinated reactive power control strategy in which STATCOM and doubly fed induction generators in wind power plants are used in order to bring back the voltage at the point of common coupling in the allowable range. First, reactive power requirements that the wind farms have to fulfill in some European countries are introduced. Second, the reactive power limitations of 2MW doubly fed induction generator are determined. Then, the static synchronous compensator (STATCOM) and the synchronous var compensator (SVC) FACTS (Flexible AC Transmission Systems) devices are presented. Finaly, various reactive power control strategies are applied to 10 MW wind farm, and the simulation results are analysed and compared

Application of STATCOM for improved dynamic performance of wind farms in a power grid

This thesis investigates the use of a Static Synchronous Compensator (STATCOM) along with wind farms for the purpose of stabilizing the grid voltage after grid-side disturbances such as a three phase short circuit fault, temporary trip of a wind turbine and sudden load changes. The strategy focuses on a fundamental grid operational requirement to maintain proper voltages at the point of common coupling by regulating voltage. The DC voltage at individual wind turbine (WT) inverters is also stabilized to facilitate continuous operation of wind turbines during disturbances --Abstract, page iii

The Control of DFIG for MPPT and application of STATCOM for grid stability

Themodeling, analysis, control and simulation of DFIG based WECS along with STATCOM implementation to the grid is presented in this paper. To maintain DC bus voltage the GVO control method is adopted in GSC for reactive power is provided. The efficient control of active and reactive power is provided through SVO scheme in RSC. The MPPT is achieved by keeping TSR to the optimum value.In this project implementation of STATCOM to grid system is shown in order to improve voltage stability during the grid disturbances. The three phase symmetrical fault is created in the distribution system and STATCOM which is connected to distribution system regulates the voltage drop and overcurrent to normal condition. The developed system is simulated for different wind speeds and allows power distribution system to be in-service during faults. The hardware prototype consists of voltage source converter and its controls are developed to verify the results